Monday, December 25, 2006

The Anthropic Cosmological Principle meets Computational Complexity; Hilarity Ensues

Scott Aaronson, the second-most amusing person in string theory, demonstrates how to solve NP-complete problems, about halfway through a talk:

But what could NP-hardness possibly have to do with the Anthropic Principle? Well, when I talked before about computational complexity, I forgot to tell you that there's at least one foolproof way to solve NP-complete problems in polynomial time. The method is this: first guess a solution at random, say by measuring electron spins. Then, if the solution is wrong, kill yourself! If you accept the many-worlds interpretation of quantum mechanics, then there's certainly some branch of the wavefunction where you guessed right, and that's the only branch where you're around to ask whether you guessed right! It's a wonder more people don't try this.

This is a pretty obvious idea once you hear it (those are always the best ones. As Huxley was suppoed to have said upon reading The Origin of Species, "How extremely stupid not to have thought of that").

Aaronson takes this as evidence that anthropic arguments are invalid, since he's fairly attached to the idea that NP-hard problems are hard. I tend to agree, there has always been something Panglossian about anthropic cosmology. In could implement Dr. Pangloss using Aaronson's procedure. If you are convinced that the world is not as good as it could be, you kill yourself. Then the versions of you left alive are perforce inhabiting the best of all possible worlds.

1 comment:

island said...

The WAP isn't even a cosmological principle, since it says virtually nothing about the structure and dynamics of our universe from first principles, but I could correct you guys all day long and it wouldn't make any difference to your opinion, so I'll have to make due with exposing your ignorance instead.